Alcoholism heritability has been established in both men and women, but, as for other complex psychiatric diseases, it has proved difficult to map genes. We have identified an intermediate marker for alcoholism vulnerability, the low voltage alpha (LVA) EEG, a normal, traitlike heritable variant of the resting EEG, present in 4-11% of the population, in which the alpha rhythm is virtually absent. We now have a complete data set, including EEG and ERP phenotypes, blind-rated DSM-III-R diagnoses, psychometric tests and DNA on 247 individuals from Bethesda, MD. We have shown that in these subjects, LVA is associated with alcoholism, particularly when accompanied by anxiety disorders (Enoch et al 1995,1999). We have found that LVA individuals have reduced amplitude P300 ERPs, further strengthening our argument for the association of LVA with alcoholism vulnerability. In order to obtain sufficient power to map genes for alcoholism, the focus of this study shifted to a Plains American Indian tribe which has a high prevalence of alcoholism. We now have EEGs and ERPs on 374 tribal members from large pedigrees and have almost completed the data set of blind-rated DSM-III-R psychiatric diagnoses and DNA from these individuals. Preliminary studies confirm the relationship of LVA with alcoholism. We will soon be in a position to start analyses for mapping genes for alcoholism. Formerly titled "Genetic studies of the electroencephalogram and event-related potentials."